Spruce is the most commonly used structural timber, sourced from the Norway spruce (Picea abies). It is light, affordable, easy to work with, and available everywhere. Virtually all joists, rafters, battens, and strips in a building structure are made of spruce.
Properties
| Property | Spruce |
|---|---|
| Durability class | IV-V (not durable outdoors) |
| Colour | Light yellow to white |
| Density | ±450 kg/m³ |
| Workability | Very good |
| Price | Low (cheapest structural timber) |
| Strength | Sufficient for structural use |
Where is spruce used?
Spruce is the workhorse of construction:
| Application | Example |
|---|---|
| Roof structure | Rafters, purlins, trusses |
| Timber frame | Studs, rails, top plate, bottom plate |
| Battening | Behind plasterboard, for insulation |
| Formwork | Temporary timber for concrete pouring |
| Interior trim | Tongue-and-groove boards, skirting, mouldings |
| Furniture | Budget furniture (painted) |
Spruce outdoors
Untreated spruce is not suitable for outdoor use. It rots within 2-5 years. Solutions:
- Pressure-treated — Treated under pressure, lasts 15-20 years
- Painted — Good covering exterior paint, repaint every 5-7 years
- Structurally protected — If the wood stays dry (under a roof cover), it lasts longer
For unprotected outdoor applications, Douglas fir, larch, or hardwood are a better choice.
Spruce vs. pine
| Spruce | Pine | |
|---|---|---|
| Tree | Norway spruce | Scots pine |
| Colour | Lighter, whiter | More yellow, more grain |
| Knots | Smaller, lighter knots | Larger, darker knots |
| Resin content | Less | More |
| Price | Comparable | Comparable |
| Application | Structural timber | Furniture, floorboards, decorative work |
In practice, spruce and pine are often used interchangeably. The difference is small.
Standard dimensions (planed)
| Dimension (mm) | Typical application |
|---|---|
| 22 x 50 | Battens, strips |
| 30 x 50 | Battening |
| 45 x 70 | Battening (heavier) |
| 50 x 150 | Rafters, light beams |
| 63 x 175 | Rafters, purlins |
| 75 x 200 | Purlins, beams |
| 75 x 225 | Heavy beams |
Related terms
- Softwood
- Douglas fir
- Pressure-treated wood
- Scaffold wood
- Larch
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